The polymerization of 2-pyrrolidone utilizing quaternary ammonium compounds to accelerate the polymerization is fully disclosed in our co-pending application Ser. No. 039,773. This invention relates to the recovery and re-use of both the unpolymerized 2-pyrrolidone and the quaternary ammonium accelerator.
At the end of the polymerization, whether for a short or lomg time, there is always some unpolymerized 2-pyrrolidone remaining in the polymer which is usually removed by washing the comminuted polymer with water or other solvent. If a quaternary ammonium accelerator is used this is also present in the polymer and must be removed by washing.
The recovery of the 2-pyrrolidone from the wash water presents no particular problem since it will withstand the temperatures involved in removing the water by distillation. But when the quaternary ammonium compound is also present, thermal stability problems arise and special methods must be devised to prevent decomposition which would result not only in the loss of some of the quaternary ammonium accelerator, but worse, cause the formation of decomposition products which act as inhibitors to the polymerization.
It is accordingly an object of this invention to provide a method or methods of recovering and re-using both the unpolymerized 2-pyrrolidone and the quaternary ammonium accelerator.